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Colon Cancer Screenings Work, Twin Studies Report

WEDNESDAY, Sept. 18 (HealthDay News) -- People are less likely to die from colon cancer if they use any of the currently recommended screening procedures, a pair of new long-term studies reveal.

Colonoscopy remains the most effective screening tool, reducing the risk of colon cancer death by 56 percent, according to new data published in the Sept. 29 issue of the New England Journal of Medicine.

Two other recommended screening methods, however, also greatly reduce colon cancer mortality, the researchers found. Flexible sigmoidoscopy provides a 40 percent lower risk of dying from colon cancer, while annual fecal blood testing offers a 32 percent reduced death risk.

"The inclusion of all these tests in the guidelines of major organizations continues to make sense," said Dr. Durado Brooks, director of prostate and colorectal cancers for the American Cancer Society. "Quite honestly, many patients don't have access to colonoscopy or are not willing to undergo a screening colonoscopy. Many studies have shown that offering patients options will increase the likelihood that they will complete some form of screening, and that is what is most important."

The results come from a pair of studies testing the long-term health benefits of screening for colon cancer.

The first study investigated the use of colonoscopy and flexible sigmoidoscopy among a group of almost 89,000 health professionals during a 20-year period.

Colonoscopy uses a thin tube equipped with a camera to examine the entire length of the colon in a procedure for which patients are usually sedated. Flexible sigmoidoscopy is a similar procedure but with a shorter tube that examines less of the colon, so patients do not have to be sedated.

The study found colonoscopy was more effective in preventing cancer throughout the entire colon, but that both procedures greatly reduced the overall risk of colon cancer death, said Dr. Andrew Chan, an assistant professor at the Massachusetts General Hospital Gastrointestinal Unit and the co-senior author of the report.

"Colonoscopy was superior to flexible sigmoidoscopy in terms of reducing the risk of colon cancer throughout the colon," Chan said. "But this study really does support the existing guidelines and recommendations for individuals to undergo screening with either colonoscopy or sigmoidoscopy. I think this study shows there's a very real impact on the risk of developing cancer and dying of cancer."

The second study focused on the fecal occult blood test, which uses chemical agents to detect trace amounts of blood in a person's stool.

Researchers led by Dr. Aasma Shaukat of the VA Medical Center and University of Minnesota, Minneapolis, followed up on more than 46,500 Minnesotans who had been randomly assigned either to undergo fecal testing every year or every other year, or receive no testing. The research ran from 1976 through 1982 and from 1986 through 1992.

The study team used death records to see which of the original study participants had died of colon cancer by 2008.

Those who underwent annual testing had a 32 percent reduced risk of colon cancer death, while biennial testing reduced colon cancer death rates by 22 percent, researchers reported.

Brooks said the fecal blood test findings were "of particular importance, because there is the perception among many primary-care clinicians that by offering patients the stool test they are somehow offering them an inferior test."

Patients who now undergo a fecal blood test should expect to see even better protection from cancer, said Dr. Theodore Levin, who wrote an editorial accompanying the two studies in the journal. Levin is an assistant clinical professor of medicine at the University of California, San Francisco.

"The old fecal blood test that was done in the Minnesota trial has been improved and enhanced through modern biochemical methods," said Levin, who also is a research scientist at the Kaiser Permanente Northern California Division of Research. "It's much more accurate and much more sensitive, so we would expect the benefit to be even greater today with that test."

The blood test may have some potential advantages over colonoscopy, Levin added.

Patients have to undergo an uncomfortable cleansing process prior to a colonoscopy using powerful laxatives, and if they fail to properly cleanse their colon, it could hamper doctors' ability to detect pre-cancerous polyps. Colonoscopy also can miss smaller lesions.

"It may be that a moderately sensitive test that is done more often will have a better chance of detecting colon cancer or preventing death from colon cancer," Levin said.

The upshot of all this is that everyone should use at least one of these screening methods as recommended, Brooks said. Experts recommend that people get a colonoscopy every 10 years, flexible sigmoidoscopy every five years or fecal blood testing every year.

"My hope is people will see these studies and realize there is potential value in all these tests," Brooks said. "Choosing any one of them is far superior to not being tested."

More information

For more information on colon cancer screening, visit the U.S. National Cancer Institute.

SOURCES: Andrew Chan, assistant professor, Gastrointestinal Unit, Massachusetts General Hospital, Boston; Theodore Levin, M.D., research scientist, Kaiser Permanente Northern California Division of Research, and assistant clinical professor of medicine, University of California, San Francisco; Durado Brooks, M.D., director of prostate or colorectal cancers, American Cancer Society; Sept. 29, 2013, New England Journal of Medicine

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